Hitherto, alloy powders of platinum and iridium, rhodium, and/or palladium have been used in high-temperature corrosive uses such as automobile exhaust gas catalysts and sensors. Recently, with downsizing and the like of products such as sensor and contact, it is required for the alloy powders to have a desired particle diameter and also to be sharp in particle size distribution.
Patent Document 1 discloses a method for producing a platinum-rhodium alloy powder by mixing a platinum fine powder or a platinum compound fine powder, a rhodium fine powder or a rhodium compound fine powder, and a calcium carbonate powder, followed by a heat treatment.
Moreover, Patent Document 2 discloses a method for producing a noble metal fine powder comprising a step of obtaining an aggregate of noble metal fine particles, a step of obtaining a mixture containing disintegrated noble metal fine particles by disintegrating the aggregate of the noble metal fine powder together with at least one of alkali metal carbonate salt and alkaline-earth metal carbonate salt, and a step of obtaining noble metal fine particles by heat-treating the mixture at 1000° C. or higher in an inert gas atmosphere and subsequently treating the heat-treated product with an acid.